Symmetrical trisazo sequential free radical initiators having two different azo functions

ABSTRACT

Polyazo compounds having at least one azo function different from the other azo function(s). Examples: 4-Ethoxycarbonylazo-4-cyanopentyl 4-T-BUTYLAZO-4-CYANOVALERATE; 2,2&#39;&#39;-Azobis(2-(4-t-butylazo-y-cyanovaleroyloxy)-4-methylpentane) . Organic syntheses requiring free radical generation in two stages are carried out using as the source of sequential free radicals a polyazo compound, as defined, wherein at least one azo function is ruptured in the first stage and the remaining azo function(s) are ruptured in the second stage. Example: Styrene monomer and 4-ethoxycarbonylazo-4-cyanopentyl 4-t-butylazo-4-cyanovalerate were reacted at about 76*C. to obtain a polystyrene containing functional azo groups. The polystyrene-azo polymer was reacted with methyl methacrylate monomer at 130*C. to obtain a block copolymer of polystyrene and poly(methyl methacrylate).

Unite States Sheppard et al.

atent 1 [451 Feb. 25, 1975 [76] Inventors: Chester Stephen Sheppard, 726

Parkhurst Blvd., Tonawanda, N.Y. 14150; Ronald Edward MacLeay, l0 Mahogany Dr., Williamsville, N.Y. 14221 [22] Filed: Feb. 22, 1972 [21] Appl. No.: 228,242

Related US. Application Data [62] Division of Ser. No. 752,752, Aug. 15, 1968, Pat. No.

[52] US. Cl 260/173, 260/86.1,260/93.7, 260/152, 260/153, 260/157, 260/169, 260/174, 260/192, 260/873, 260/878 [51] Int. CI....C07c 107/02, C070 107/04, C08f 19/10 OTHER PUBLICATIONS Rabjohn, J. Am. Chem. Soc., Vol. 70, p. 1181-1183, (1948).

Primary ExaminerF1oyd D. I-Iigel [57] ABSTRACT Polyazo compounds having at least one azo function different from the other azo function(s). Examples:

4-Ethoxycarbonylazo-4-cyanopentyl 4-t-butylazo-4-cyanovalerate; 2,2-Azobis[2-(4-t-butylazo-y-cyanovaleroyloxy)-4- methylpentane]. Organic syntheses requiring free radical generation in two stages are carried out using as the source of sequential free radicals a polyazo compound, as defined, wherein at least one azo function is ruptured in the first stage and the remaining azo function(s) are ruptured in the second stage.

Example: Styrene monomer and 4-ethoxycarbonylazo- 4-cyanopentyl 4-t-butylazo-4-cyanovalerate were reacted at about 76C. to obtain a polystyrene containing functional azo groups. The polystyrene-azo polymer was reacted with methyl methacrylate monomer at 130C. to obtain a block copolymer of polystyrene and po1y(methyl methacrylate).

5 Claims, N0 Drawings SYMMETRICAL TRISAZO SEQUENTIAL FREE RADICAL INITIATORS HAVING TWO DIFFERENT AZO FUNCTIONS This is a division of application Ser. No. 752,752, filed Aug. 15, 1968, now U.S. Pat. No. 3,649,614 issued Mar. 14, 1972.

BACKGROUND OF THE INVENTION 1. The Field of the Invention 'lhis invention relates to new polyazo compounds wherein at least two different azo functions are present. Also the invention relates to a method of providing free radicals in sequence wherein a novel polyazo com- 0 R O T I ll RS -o-?- N-C- l l o R s 0 P. ll 1 R-C- n-c- 1 pound, as defined, is used as the source of sequential free radicals. More particularly the invention relates to the preparation of vinyl polymers containing functional azo groups and to block copolymerization using such 35 vinyl-azo polymers.

SUMMARY OF THE INVENTION aliphatic. aromatic. and heterocyclic:

27 C and C are different and may he the same when A and A are different; 3. A and A are biradicals selected from the class consisting of 2. The Prior Art Compounds having more than one azo function have been reported but in all cases the azo functions are identical. Sequential free radical generation would not s be observed with the prior art compounds. Such prior 4. A and A are different, and may be the same when C and C are different in l, and may be the same when A and C are different in l";

5. B is a biradical selected from the class consisting O O O H O H 0 llll ll 1 ll 1 ll C-O- O -CQ-,, -C-N -O-C-N- -S-C art is reported in: U.S. Pat. No. 2,554,141; U.S. Pat. 65 -O, S, R and a direct bond;

No. 3,244,692; Neugebauer et al, Ann. 706, 107 (1967); Bellamy et al, J. Chem. Soc. C, 1966, 1989; Easer et al, Gummi 11, WT 57-62 (1958).

6. X is an inorganic anion; 7. Z is a monovalent radical selected from the class consisting of 3,868,359 3 a 4 -CN, -o1, -31; 41 -oc:t, -sct\ ooxT-rg, 4:0 -No,,

0 (6 NH NH R O J R it I l l l v -o -o-2f s- -ocm, 0 R

ll C R N==C-l .d -N\ C 0-0 ll ll 0 O O O O O a i 0 OR OR E ii 1| H 5; II I l l 'l l l l i -c-rt -c -c-c-. 0-0 -0 C-, --c-?, -c-, -C--?, --C,

l l l I R R R R R R R I? R R R R A l -C-R (i-R -C- --R C- and -R and l l i i I l I l 0 g 0 0 O= i "O O=Ci C=O ii 0 ti 1i til (i1 0 Pt-iim EH I-R 8. R is a hydrogen, aliphatic, cycloaliphatic, aro- 16. M is an ion selected from the class consisting of mutic, or heterocyclic radical; alkali metal, alkaline earth metal, and NH 9. R is an aliphatic, cycloaliphatic, aromatic or het- Another aspect of the invention is a method of precrocyclic radical; 45 paring a block polymer which method consists essen- 10. R is a lower alkyl radical; tially of: (l) forming a polymer having azo functions I 1. R is an aliphatic, cycloaliphatic or aromatic radipre ent by reacting vinyl monomer and a polyazo coml; pound I under vinyl polymerization conditions, control- 12. R is a tertia aliph ti r di l; ling conditions in order to cause one azo function to 13. R is an ali hati l li h ti or aromatic 50 rupture leaving another azo function intact, said rupbi di l; ture of the one azo function having the effect of initiatl4. R and R individually are monovalent radicals ing d p y n; and (2) reacting, vinyl-type Selected f the'class consisting f monomer with the polymer of step (1) under condio o "0 o 0 bit "a !l 11 ll u u H I 1 -c oa, -C-O3 -c-0 r. -C-R- -c-c1, -C-N-R, -(l)-OR,

C R o R R 0 a R 0 ll i i l l ii i i ll -Q-Br, and CIO-CR, -(lJ-O-C 1, -C-O- -I -Cl1-O-COR, -CN, @10 l R R R R l5. R and R taken together are biradicals selected tions to rupture the azo-carbon linkages of said step (1) from the class consisting of polymer to produce a block polymer product.

Example: (1) reacting styrene with an initiating amount of the ester of 2-hydroxyethyl tbutylazocarboxylate and 4-t-butylazo-4-cyanovaleryl chloride in a nitrogen atmosphere at 65C for about hours; and (2) reacting methyl methacrylate with the azo containing polystyrene of step (1) in a nitrogen atmosphere at 130C for about 3 hours to obtain a polystyrene-poly(methyl methacrylate) block polymer.

DESCRIPTION OF THE INVENTION AND WORKING EXAMPLES The Polyazo Compounds The novel azo compounds are defined in I supra, and alternatively in l' and I". In the formula aliphatic and cycloaliphatic are used in their broadest technical meaning; however, it is to be understood that substituents which may be present in the aliphatic or cycloaliphatic radical must be inert to the azo functions, so as not to interfere with the preparation reaction(s). Commonly the aliphatic radical will have 1-36 carbon atoms, usually 1-22, and the cycloaliphatic radical will have 3-12 ring carbon atoms, usually 4-8, in a single ring compound and 5-24 ring carbon atoms, usually 6-12, in a doubled or fused ring radical. It is to be understood that both aliphatic and cycloaliphatic may be substituted with aromatic group(s).

Aromatic is used in its broadest technical meaning and includes a single benzoid ring, doubled (and higher) rings, and fused rings. These may be substituted with groups which are inert to the azo functions or by one or more non-aromatic rings, including fused rings. Commonly these are phenyl, naphthyl and biphenyl radicals.

Heterocyclic is used in its broadest technical meaning of a ring made up of carbon atoms and at least one other atom, such as oxygen, sulfur and nitrogen. Substituents in the ring are inert to the azo functions.

The above definitions are broad and intentionally so because the defined Rs and Zs appearing in the radical definitions of the azo compounds of Formula I do not affect the general utility of the compounds or the ability to make the compound by the processes set forth herein. Numerous compounds coming within Formula I are set out in the working examples.

A tertiary aliphatic radical is one where the free valence is associated with a carbon atom which is joined directly through its other valences with three other carbon atoms, for example, a t-butyl radical.

Lower alkyl is intended to have about l-12 carbon atoms and usually 1-8 carbon atoms, preferably 1-6 carbon atoms. Alkyl, Alkenyl, and Alkynyl: Each alkyl group may include 1 or more carbon atoms. Desirably each has 1-22 carbon atoms.

CH 0 CH Cycloalkyl and cycloalkenyl: May be single ring or have two or more fused rings. Desirably the single ring has in the ring 3-12 carbon atoms, and preferably 5-8 carbon atoms. Preferably the total number of carbon atom in the radical is 5-12. Cyclopentyl, cyclohexyl, and the radical corresponding to decalin are preferred radicals.

Aryl:

May be a single benzene ring, or a doubled or higher system, e.g. biphenyl, terphenyl, quaternaphthalene, or a fused benzene ring system, e.g. naphthalene, anthracene, phenanthrene, or an alkane bridged system, e.g., biphenylmethane, biphenylpropane. Phenyl, biphenyl, naphthalyl and the alkyl substituted radicals are preferred Aralkyl:

The Ar portion of the radical may be as in Aryl. The alkyl" portion has desirably l-l2 carbon atoms and preferably 1-6 carbon atoms.

The preferred definitions of R's R is H, alkyl, alkenyl, aralkyl, Cycloalkyl, phenyl, naphthyl, or heterocyclic having carbon and at least one 0, S, or N in the ring.

R is alkyl, alkenyl, aralkyl, cycloalkyl, phenyl, naphthyl, or heterocyclic having carbon and at least one O, S, or N in the ring.

R is alkyl, alkenyl, aralkyl, cycloalkyl, phenyl, or naphthyl.

R is t-alkyl, t-alkenyl or t-aralkyl.

R is a divalent radical of saturated, ethylenically unsaturated or acetylenically unsaturated aliphatic or cycloaliphatic hydrocarbons, or benzene or naphthalene hydrocarbons or biphenyl hydrocarbons.

It is to be understood that the above preferred definitions include the carbon atom limitations previously set out with respect to the various R's.

X is an inorganic anion. Anions derived from the mineral acids are preferred. Illustrative are F. Cl. Br, HSO SO,=, H PO HPO PO CIO ClO CN, NO NO;, and CO M is alkali metal, alkaline earth metal or ammonium (NHf). Illustrative are: Li, Na, K, Ca, Sr and Ba. Any compound which contains more than one azo group (excluding diaromatic azo groups) and at least two of the azo groups vary in their physical or chemical properties will be capable of sequential free radical initiation. The preparations of some typical such compounds are given in Example I to XIII. The following are a few of the many other such compounds that are capable of sequential free radical generation according to the present invention: A

o ll

Utility The polyazo compounds of this invention may be used in any operation or reaction requiring free radicals such as: in organic syntheses, either as free radical reactants or initiators; polymerization of vinyl monomers to form either homopolymers or copolymers; flame retardant synergists with bromine compounds for polymers such as polystyrene; curing agents or crosslinking agents for elastomers such as natural and synthetic rubbers. silicone gums, polyolefm copolymers, and the like; and curing agents for thermosetting resins such as unsaturated polyester-vinyl monomer blends, polyolefins and the like.

The polyazo compounds of this invention evolve considerable amounts of gases, such as nitrogen, upon decomposition and are therefore also useful as blowing or foaming agents for preparing foamed polymers.

The polyazo compounds of this invention that contain a carbonyl group directly linked to one or more of the azo nitrogens are also useful as selective oxidizing agents and as chemical reactants. These types of azo compounds contain reactive azo groups that are dienophiles in Diels Alder reactions and to which many compounds containing active hydrogen atoms can be added. 3

The preferred use of the polyazo compounds of this invention is for the sequential generation of free radicals. An especially preferred use is polymerization of vinyl monomers in sequence to form first, an azocontaining polymer and subsequently. by polymerizing further with other vinyl monomers, block copolymers.

The azo function on the azo-containing polymer initially formed above can also be used to generate a free radical site on the polymer for other applications such as: crosslinking, grafting, adhesion, lamination, and attaching other functions to the polymer which would impart desirable properties such as dyeability; antistatic; and light, heat and/or oxidative stability.

Such azo-containing polymers can be stored, shipped and handled prior to the subsequent operation for any length of time desired provided that the polymer is not subjected to conditions that will cause the azo function to decompose or rupture prematurely.

Sequential generation of free radicals is also useful in other applications such as in the homopolymerization of monomers such as styrene and ethylene.

Another application is to use one or more of the azo functions to gel a resin such as an unsaturated polyester-vinyl monomer blend and to use the other azo function(s) to subsequently cure the resin.

Other applications for sequential free radical generation from the novel polyazo compounds of this invention will become apparent to those skilled in the art.

Methods of Polymerization The method inventions are directed to the use of compounds of the invention to prepare block polymers by a sequential procedure wherein a compound I is used to initiate vinyl polymerization to prepare a polymer including an azo function as a part of the polymer. The azo containing polymer is then further polymerized with vinyl monomer under conditions to rupture the azo function whereby the block polymer is formed. These novel compounds are useful as sequential free radical generators, i.e. one or more of the azo groups can be preferentially decomposed to generate free radicals for a particular application (e.g. vinyl monomer polymerization) keeping at least one azo group substantially undecomposed for a later application (e.g. formation of a block copolymer with another vinyl monomer polymerization) and vice-versa. These sequential and/or preferential decompositions of the azo portions of the molecule can be accomplished for example by taking advantage of the difference in the thermal rates of decomposition of the various azo portions of the molecule. A second method, also based on the different thermal rates of decomposition is to use the same temperature but different reaction times.

A third method would be to decompose the azos photolytically taking advantage of the difference in wavelength of the ultraviolet maximum for conjugated and nonconjugated azos. This technique would require that at least one of the azo groups is conjugated and at least Thus, by taking advantage of the differences in the physical and chemical properties of the azo groups contained in the novel dior polyazo compound of structure l, a variety of techniques can be used for sequential free radical generation.

Sequential free radical generation is very useful in the vinyl polymerization field. Block copolymers can be made from any combination of polymerizable vinyl monomers. Sequential free radical generation is also l0 employed in the conventional polymerization of ethylene and styrene. The present art accomplishes this by using two or more polymerization initiators of different thermal stability.

Conventional polymerization techniques, i.e. bulk,

solution, suspension or emulsion polymerization, can

temperature (or exotherm) control, etc.

one of the azo groups is not conjugated. A fourth method would be to decompose at least one ofthe azos photolytically, taking advantage of the difference in wavelength of the ultraviolet maximum for conjugated and nonconjugated azos, and then decompose the other azo(s) thermally or vice-versa. Again this method requires a difference in the wavelengths of ultraviolet absorption. A fifth method would be to activate an azoester or azoamide portion of the molecule with a Lewis acid and then decompose the other azo(s) thermally or photolytically in a second step or vice-versa. A sixth method would be to activate an azoester or azoamide portion of the molecule by hydrolysis and then decompose the other azo(s) thermally or photolytically in a second step or vice-versa. The last two methods require that at least one of the azo groups is an azoester or an azoamide and that at least one of the azo groups is not an azoester or an azoamide.

The temperatures at which the polymerizations are carried out will depend upon the polymerization tech- 'nique; the monomer, solvent or suspending medium; and the physical properties desired in the polymer; but most of all upon the sequential azo initiator and the method chosen to decompose the various azo portions of the initiator. Activation of azo esters and azo amides 'with Lewis acids can be used to lower their decomposition temperatures to room temperature. Activation of azo esters by hydrolysis can be used to lower their decomposition temperatures to the freezing point of the aqueous solution. The decomposition rates of the various azo groups upon exposure to ultraviolet irradiation will be dependent upon the wavelength of the ultraviolet source. Conjugated azos such as azo esters and azo amides absorb ultraviolet light much stronger and absorb at a higher wavelength than the aliphatic azos. Consequently the conjugated azos can be preferentially decomposed in the presence of the aliphatic azo by using a wavelength corresponding to the wavelength of the ultraviolet maximum for the conjugated azo or vice versa.

The temperatures used for the thermal decompositions of the various azo portions of the initiator will depend upon the thermal stability (half-life) of the various azo groupings in the molecule. These half-lives may be determined quantitatively for each sequential azo initiator by conventional methods, i.e. gas evolution. ultra-violet or gas chromatographic analytical techniques, to determine the rate of disappearance of each azo group at any given temperature. However it is not necessary to accurately determine the half-like of each portion since most half-lives can be predicted, within a few degrees, from the analogous monomeric azo compounds. Some ten-hour half-life temperature ranges of some typical azo structures are given in Table I. More accurate data is available on the individual compounds where R, R and R" are known and such data was used to estimate the ten-hour half-lives on the compounds prepared in Examples I to XIII.

All the vinyl monomers listed can be polymerized by azo initiators'Azo initiators are commonly used in all four free-radical polymerization techniques. It is old in the art to initiate polymerization of vinyl monomers with azo initiators by irradiating the monomer-initiator solution with an ultraviolet source. It is also old in the art to activate azo esters and amides with Lewis acids.

General Structure 10 Hour 12, Range t CH- CH3 l g (CH C-N=N-C 2-CH2-$-CH3 105 to it, 011

I R-(g-h-Iv-R R R! 1..c, 90

CH3 CH3 c H l: -:=x- -CH3 55 g 03 on The expression vinyl monomer includes all those organic compounds containing at least one group in their molecule. Examples of these monomers are styrene, ethylene alpha-methylstyrene, dichlorostyrene, vinyl naphthalene, vinyl phenol, acrylic acid and the alpha-alkyl substituted acrylic acids; the esters of these unsaturated acids, such as methyl acrylate, methyl methacrylate, butyl methacrylate, and propyl acrylate, the vinylidene halides, such as vinylidene chloride. vinylidene bromide and vinylidene fluoride; vinyl esters of the in ganic acids, such as the halogen acids and hydrocyanic acid, as vinyl chloride. vinyl bromide, acrylonitrile, and methacrylonitrile; the vinyl esters of the monocarboxylic acids, such as vinyl acetate. vinyl chloroacetate, vinyl benzoate vinyl valerate, and vinyl caproate; the vinyl esters of the polycarboxylic acids, such as divinyl succinate, divinyl adipate, vinyl allyl phthalate, vinyl methallyl pimelate, and vinyl methyl glutarate; the vinyl esters of the unsaturated acids such as vinyl acrylate, vinyl crotonate, and vinyl methacrylate; the vinyl ethers, such as vinyl ethyl ether, vinyl butyl ether, and vinyl allyl ether; the vinyl ketones, such as vinyl butyl ketone, and vinyl ethyl ketone; and the allyl derivatives, such as allyl acetate, allyl butyrate, diallyl phthalate, diallyl adiphate, methallyl 'propionate, allyl chloride, methallyl chloride ally acrylate, methallyl methacrylate, and dienes such as butadiene and chloroprene.

Azo initiators are also effective initiators for the copolymerization of the above-described compounds with each other or with other types of polymerizable organic compounds, particularly those containing at least one ethylenic linkage, such as the saturated esters and polyesters of the unsaturated acids, such as the maleates, fumarates, crotonates, and the like.

Other method inventions are directed to the use of the novel compounds of the invention to gel and cure a resin such as an unsaturated polyester-vinyl monomer blend by a sequential procedure wherein one or more like azo functions of a compound I are preferentially decomposed to cause the the resin to gel and subsequently decomposing the remaining azo functions thereby causing the gelled resin to be cured to a hard thcrmoset. This allows for intermediate storage. shaping, and handling of the gelled resin before curing. cvg. as in matched metal die molding.

Gelling resins, such as unsaturated polyestervinyl monomer blends with free radical initiators, without curing, can be accomplished in several ways: 1) Using initiators that will gel but not cure the resin; 2) Using very low concentrations of initiators; 3) Using and controlling temperatures below those normally used for optimum curing; and 4) Using free radical scavengers, e.g. excessive amounts of antioxidants, which diminish the efficiency of the initiator and prevent curing of the resin. By the judicious choice of the polyazo compound and the gelling and curing conditions, the polyazo compounds of the invention may be used for sequentiall gelling and curing resins such as unsaturated polyestervinyl monomer blends.

For example, it has been found that certain azo structures, e.g. those containing a hydroxyl group attached directly to the carbon atom bearing the azo nitrogen atom, will gel, but not cure, an unsaturated polyestervinyl monomer resin blend at relatively low temperatures. Compounds containing this type of functional group in conjunction with another azo structure which will cure the polyester resin blend, such as the compound of Example XlX and compounds 43 and 44, can be used in this particular application.

Unsaturated polyester-vinyl monomer resin blends containing the usual fillers, extenders, or reinforcing agents used by the art, such as in polyester premix or prepreg materials may be used with the polyazo compounds of this invention.

The improvement of the method invention is that both the gelling and the curing portions ofthe complete initiator system is provided in a single compound, namely one of the novel polyazo compounds of the invention. Previously, two separate and distinct initiator systems had to be used, one for gelling and the other for curing. In some cases a single initiator is used and the process is interrupted at the gelled stage by cooling, wherein the initiator is only partly decomposed and subsequently cured with the remaining undecomposed initiator. This latter process presents serious problems. Because of the highly exothermic nature of the gelling and curing steps, control and reproducibility are extremely difficult to achieve when using an initiator containing only like free radical generating structures.

EXAMPLE 1 Preparation of 4-Ethoxyearbonylazo-4-cyanopentyl 4-t-Butylazo-4-cyanovalerate o ctr o ctr stirred overnight. The next morning the aqueous layer was saturated with NaCl and extracted 3 times with CH CI The CH Cl extracts were combined, dried over anhydrous Na SO filtered and the CH CL 5 stripped off. The yield was 12.3 g. (60%). The infrared spectrum was in agreement with the structure of 2- ethoxycarbonylhydrazo-Z-cyano-S-hydroxypentane.

To a solution of 5.0 g. (.025 mole) of 2- ethoxycarbonylhydrazo-2-cyano-5;hydroxy-pentane and 4 g. of pyridine in 25 ml. of ether was added 5.5 g. (.025 mole) of 4-t-butylazo-4-cyanovaleryl chloride. The reaction was stirred an additional hour and poured into 50 ml. water. The ether layer was separated, washed 3 times with water, dried over anhydrous Na S filtered and the ether stripped off. The yield was 8.5 g. (85.5%). The infrared spectrum of the product was in agreement with the structure of 4- ethoxycarbonylhydrazo-4-cyanopenty1 4-t-butylazo-4- cyanovalerate.

The above hydrazo (8.5 g. or .0216 moles) was slurried in 25 ml. water in a 250 ml. round bottom flask, 50 ml. of CH Cl added and the mixture cooled to 5C. in an ice bath. Chlorine was passed into the mixture at approximately 0.3 g. minute until 1.6 g. (.0225 moles) was absorbed. The reaction was stirred an additional minutes, the CH Cl layer separated. washed once with water, twice with saturated NaHCO once with satua Formula I where: n 1;

The azoester portion of the molecule has a 10 hour half-life at approximately 130C. while the di-aliphatic azo portion has a 10 hour half-life at approximately i 76C. 0 0 1K 00; A -C-(CH,) EXAMPLE n g N '45 Preparation of 4-Carbamylazo-4-cyanopentyl 4-t-Butylazo-4-cyanovalerate i l f Ni' --c-N=ni-(ca 3 -ocer -C-N=N-C- (ctr i 0 CH Formula 1 where: n l;

n A B A 0 ca n L 6 c e Na a-- A -d-(ca,)

-c(ca O N To a mixture of 10.4 g. (0.1 mole) ofethyl carbazate, 10.2 g. (0.1 mole) of 3-acetyl-1-propanol, 4.9 g. (0.1 o H mole) sodium cyanide and 40 ml. water was added 10 a g. of concentrated H 50 diluted with 20 ml. water. 3 ...0 g-; A ..(CH C The mixture immediately began to warmup. The flask was stoppered with a pressure release stopper and 27 -c(cn Formula I where:

with NaHCO solution, once with saturated NaCl solution, dried over Na SO filtered and the CH Cl stripped off. The yield was 4.7 g. (81%) of a yellow liqsaturated NaCl solution, dried over anhydrous Na SO filtered and the Cl-l Cl stripped off. The yield was 2.2 g. of a viscous yellow liquid. The infrared spectrum of the product was in agreement with the structure of 2-carbamylazo-2-cyano-5-hydroxypentane.

The 2-carbamylazo-2-cyano-5-hydroxypentane (2.2 g. or 0.0126 moles) was dissolved in 20 ml. of ether containing 2 ml. of pyridine. The solution was cooled to 15C. and 2.9 g. (0.0126 moles) of 4-t-butylazo-4- cyanovaleryl chloride was added dropwise. The reaction was stirred one-half hour after the addition was over, poured into 25 ml. water and the ether layer separated. The ether layer was washed with 5% l-lCl, water, 10% NaHCO solution, saturated NaCl colution, dried over anhydrous Na SO filtered and the ether stripped off. The yield was 4.6 g. The crude product was purified by chromatographing it over alumina using benzene as the eluent. The infrared spectrum of the purified product was in agreement with the structure of 4-carbamylazo-4-cyanopentyl 4-t-butylazo-4- cyanovalerate. The material assayed 77% by iodometric analysis.

The azoformamide portion ofthe molecule has a 10 hour half-life at approximately C. and the dialiphatic azo portion has a 10 hour half-life at approximately 76C.

EXAMPLE III Preparation of the Ester from 2-hydroxyethyl t- Butylazocarboxylate and 4-t-Butylazo-4-cyanovaleryl Chloride A mixture of5 g. (0.0567 moles) of t-butylhydrazine and 5 g. (0.0567 moles) of ethylene carbonate were heated for 7 hours in an oil bath at 50-55C. and allowed to cool overnight. The resultant product weighed 10.0 g. (100%). An infrared spectrum of the product was in agreement with the structure of 2-hydroxyethyl t-butylhydrazocarboxylate.

To a solution of 10.0 g. (.0567 moles) of 2- hydroxyethyl t-butylhydrazocarboxylate and 4 g. of pyridine in 50 ml. of ether was added 14 g. (0.06 moles) of 4-t-butylazo-4-cyanovaleryl chloride, controlling the addition rate to maintain a gentle reflux of the ether. The reaction was stirred an additional 3 hours and then poured into 50 ml. water. The ether layer was separated and poured into a 100 ml. r.b. flask, 20 ml. water added and then 4 g. (0.0567 moles) of chlorine was passed into the reaction mixture holding the temperature below 20C. with an ice bath. The reaction was stirred an additional 15 minutes. the ether layer separated. washed once with water. twice with 10% NaHCO once with saturated NaCl solution. dried over anhydrous sodium sulfate, filtered and the ether stripped off. The yield was 15.6 g. (75%) ofa yellow liquid. The indrared spectrum was in agreement with the structure of the desired product. The material assayed 98% by iodometric analysis.

The azoester portion of the molecule has a 10 hour half-life at approximately C. and the di-aliphatic azo portion has a 10 hour half-life at approximately 76C.

EXAMPLE IV Preparation of the Ester from N-(2-Hydroxyethyl)-tbutylazoformamide and 4-t-Butylazo-4-cyanovaleric acid Formula I where:

To a solution of 10.2 g. (0.0595 moles) of isopropyl dium hydroxide, 4.6 g. (0.065 moles) of chloride and t-butylazocarboxylate in 50 ml. ethanol, cooled to C., 60 ml. water] was slowly added. The temperature was added 3.62 g. of ethanolamine holding the temperslowly rose from 20 to 36C. and was maintained there ature below 10C. The reaction was stirred an addiwith a cold water bath untilthe exotherm subsided. The tional hour and then the ethanol was stripped off. The bath was removed and the temperature slowly dropped yield was 10.3 g. (100%) of a yellow liquid which asback to room temperature over 2 hours. The reaction sayed 92% by an iodometric analysis as N-2- was then allowed to stir overnight. The next morning hydroxyethyl-t butylazoformamide. the CH C1 layer was separated, washed with water,

To a solution of5 g. (0.029 moles) of the above N-2- 5% HCl, twice with saturated NaHCO solution, once hydroxyethyltbutylazoformamide and 8 g. of pyridine with saturated NaCl solution, dried, filtered and the in 50 ml. ether was added 7 g, (0,03 m l s) f 4+ methylene chloride stripped off. The yield was 8.4 g.

butylazo-4-cyanovaleryl chloride, controlling the addi- Of a a q The infrar d spectrum was in tion rate to maintain a gentle reflux of the ether. The agreement (1th the Structure of -p y reaction was stirred an additional 3 hours and then y yp poured into 25 ml. water. The ether layer was sepa- To a Solution of g- (00249 moles) of rated, washed dnee with 5% HCl, with 10% NaHCO p y y y yp and saturated NaCl solution, dried over anhydrous Na SO4, (00275 moles) of Py in 25 ether was added filtered and the ether stripped off. The yield was 10.3 gole of y -y y g, (98%) f vi ll li id Th i f d specchloride maintaining the temperature around 15C. t w i agreement i h h of the desired product. with a cold water bath. The reaction was stirred for an The azoformamide portion of the molecule has a 10 additional hour and Poured into 50 Water The hour half-life at approximately 110C. while the dialiether layer was Separated, washed with 5% L satuphatic azo portion has a 10 hour half-life at a rated Nal-lCO solution, saturated NaCl solution, dried ately 76C, over anhydrous sodium sulfate filtered and the ether evaporated. The crude product was ehromatographed EXAMPLE v over alumina and eluted with benzene. The yield was Preparation of the Ester from 2-Phenylazo-2-cyano-5- 7.5 g. (73%) ofa dark liquid. The infrared spectrum of hydroxypentane and 4-t-Butylazo-4-cyanovaleric acid the product was in agreement with thatof the desired CH; 3 CH 0 1%,;--N=N(i--(CH -oo-(ca, -C-N=N-C(CH;,

CH O

Formula. I where: n l; C C H A -(i-(CH) B -OC chi N A solution of 9.0 g. (0.047 moles) of the phcnylhyproduct. drazone of 3-acetyl-l-propanol in 15 ml. of HCN was The phenylazo linkage has a 10 hour half-life at apallowed to stand in a pressure bottle for 1 week at room proximately 130C. while the t-butylazo linkage has a temperature. The contents were poured into ice water 10 hour half-life at approximately 76C.

and the organic layer taken up in 75 ml. CH CI The CH Cl layer was washed with saturated NaHCO solu- EXAMPLE VI tion, and saturated NaCl solution. The CH Cl solution Preparation of the Diester from 2,2-Azobis( lwas then placed in a 250 ml. round bottom flask and a hydroxy-2-methylpropane) and 4-t-Butylazo-4- NaOCl solution [prepared from 6 g. (0.15 moles) of socyanovaleryl chloride CH 0 CH CH (3H (CH c-N=N-J:-(ca,) coctr,- -N=NCCl-l OC(CH -CN=N-C(CH N a 3 CN Formula. I where: n 2; c (crr c-; A -c-(crr,)

To a solution of 3.4 g. (0.0195 moles) of 2,2- azobis(l-hydroxy-2-methylpropane) and 8 g. of pyridine in 50 ml. ether, cooled to 10C., was added 10 g. (0.0435 moles) of 4-t-butylazo-4-cyanovaleryl chloride. After the addition was over, the reaction was stirred an additional 4 hours at room temperature. The reaction mixture was poured into water, the ether layer separated, washed once with 5% HCl to remove the excess pyridine, twice with 5% KOH at 5C., once with 5% HCl, followed by 10% NaHCO- and saturated sodium chloride solution. The ether solution was dried over anhydrous sodium sulfate, filtered and the ether evaporated. The yield was 8.3 g. or 81%. The product was a viscous oil whose infrared spectrum was in agreement with that of the desired product.

The material was purified by column chromatography over alumina and eluting the product with pentane. A solid was obtained which had a melting point of 6l63C. after recrystallization from eyclohexanepentane.

The external azo linkages have a 10 hour half-life at approximately 76C. while the internal am linkage has a 10 hour half-life at approximately 160C.

EXA MPLE Vll Preparation of 2,2-Azobis [2-( 4-t-butylazo-4-cyanovaleroyloxy )-4- methylpentane] CH CH CH O To a solution of 7.2 g. (.031 moles) of sodium 4-t-butylazo-4-cyanovalerate in 40 ml. of absolute methanol, cooled to 5C. in an ice bath, was added 4.01 g. (.015- moles) of 2,2-azobis(2-chloro-4- methylpentane) dropwise over 10 minutes. After the addition was complete, the reaction was stirred an additional one-half hour and poured into 200 ml. of ice water. The organic layer was extracted with pentane. the pentane layer washed with saturated NaHCO solution, saturated NaCl solution, dried over anhydrous sodium sulfate, filtered and the pentane stripped off. The yield was 4.9 g. (53%) of a light yellow liquid, whose infrared spectrum was in agreement with that of the desired product.

The two azonitrile portions of the molecule have 10 hour half-lives at approximately 76C. while the symmetrical azo-valerate portion of the molecule has a 10 hour half-life at approximately 120C.

Preparation of Di-(1-t-butylazo-l.3-dimethylbutyl) 4,4 '-A zobis( 4-cyanovalerate) l N la, (ill; on lit in CH! h ca ba ca Formula I wherez n 2; C (CH3)3C-; A ala-i o ca N B O-g A4 2- la, (la CH3, ha

ca o ca ca 0 CH3 (cn c =N-C-O-ll-CH,-CH,-C-N=N-C-CH; -cH, -C-O-CN=NC(CH3 a, v N ca H H bit on: ba

Formula. I where: n 2; C (CH C-;

ll l B= A To a solution of 3.2 g. (.01 moles) of disodium 4,4- azobis (4-cyanovalerate) in 25 ml. of absolute methan01, cooled to 5C. in an ice bath, was added 4.1 g. (.02 moles) of 2-t-butylazo-2-chloro-4-methy1pentane dropwise over minutes. After the addition was complete, the reaction was stirred an additional one-half hour and poured into 200 ml. of ice water. The organic layer was extracted with pentane, the pentane layer washed with saturated NaHCO solution, saturated NaCl solution, dried over anhydrous sodium sulfate, filtered and the pentane stripped off. The yield was 3.3 g. (54%) of a light yellow liquid, whose infrared spectrum was in agreement with that of the desired product.

The symmetrical azonitrile portion of the molecule has a 10 hour half-life at approximately 65C. while the two azo-valerate portions have 10 hour half-lives of approximately 120C.

EXAMPLE IX Preparation of l-t-Butylazo-l ,3-dimethylbutyl 4-t-butylazo-4-cyanovalerate The azonitrile portion of the molecule has a 10 hour half-life at approximately 76C. while the azo-valerate portion of the molecule has a 10 hour half-life at approximately 120C.

EXAMPLE X Preparation of the Di Ester from N-(2-hydroxyethyl)-t- H CN H a; t... 7

CH Formula I where: n 1; C (CH C-; A 3

(1H. dn CH CH 0 H; B -oii-, A Jea c -c(ca To a solution of 4.7 g. (.0201 moles) of sodium butylazoformamide and Trans-4,4-Azobis(4- 4-t-butylazo-4-cyanovalerate in 25 ml. methanol,

cyanovaleryl chloride) o cit II .ll 1

(CH3)3C- =N-C-NH-CH9 -cn -OC--CH:CH,C-N

N 1 Formula I where; n 2; c (ctr ).,c-; A -c-Nrr(cir fi ca B -oc-; A -(CH=)3-C- To a solution of 5.7 g. (.018 moles) of trans-4,4- azobis(4-cyanovaleryl chloride) and 6 ml. pyridine in ml. of ether was added 6.22 g. (.036 moles) of N-(2-hydroxyethyl)-t-butylazoformamide dissolved in 5 ml. of ether. The alcohol was added over 5 minutes maintaining a gentle reflux. After the addition was complete the reaction was refluxed gently for 15 minutes and then cooled down. The product was insoluble in ether so methylene chloride was added until the product went back into solution. The methylene chloride solution was washed with cold water, 5% HCl, saturated NaHCO solution, saturated NaCl solution dried over anhydrous Na SO filtered and the solvent evaporated off. The yield was 5.6 g. (74.6%) ofa dark yellow viscous liquid whose infrared spectrum was in agreement with that of the desired product.

The two azoformamide portions of the molecule have 10 hour half-lives at approximately 110C. while the symmetrical azonitrile portion of the molecule has a 10 hour half-life at approximately 65C.

EXAMPLE XI Preparation of the Di Ester from 2-Hydroxyethyl t- Butylazocarboxylate and Cis-4,4'-Azobis(4- cyanovaleryl chloride) in 25 ml. of ether was added 5.25 g. (0.0302 moles) of 2-hydroxyethyl t-butylazocarboxylate dissolved in 5 ml. of ether. The alcohol was added over 5 minutes maintaining a gentle reflux. After the addition was complete the reaction was refluxed gently for an additional 1 /2 hours and the pyridine hydrochloride filtered off. The ether filtrate was washed with water 5% HCl, cold water, 10% NaHCO solution and saturated NaCl solution. The ether solution was dried over Na SO filtered and the ether stripped off. The yield was 5.0 g. (79.3%) ofa dark yellow viscous liquid whose infrared spectrum was in agreement with that of the desired product.

The two azo ester portions of the molecule have 10 hour half-lives at approximately 130C. while the symmetrical azonitrile portion of the molecule has a 10 hour half-life at approximately C.

EXAMPLE Xll Preparation of the Di Ester from 2-Ethoxycarbonylazo- Formula I where: n'= 2; c (CH3)3C-; A moon -0a,; B -oc-;

To a solution of 4.78 g. (.0151 moles) of cis-4,4'- azobis(4-cyanovaleryl chloride) and 5 ml. of pyridine 2-cyuno-5-hydroxypcntane and Trans-4,4-Azohis(4- cyanovaleryl chloride) Formula I where:

To a solution of 8.20 g. (0.04 moles) of 2- ethoxycarbonylazo-2-cyano-5-hydroxypentane (prepared as in Example II) and ml. of pyridine in 50 ml. CH Cl was added 6.32 g. (0.02 moles) of trans-4,4- azobis(4-cyanovaleryl chloride) holding the temperature at 25C. 50C. The reaction was stirred for an additional 3 hours and poured into water. The CH Cl solution was washed with 5% HCl and then with water until neutral. The CH CI solution was dried over anhydrous sodium sulfate, filtered and the CH Cl removed on a rotating evaporator leaving 12.8 g. (98% yield) of a yellow viscous liquid whose infrared spectrum was in agreement with that of the desired product.

The two azo ester portions of the molecule have hour half-lives at approximately 130C. while the symmetrical azonitrile portion of the molecule has a 10 hour half-life at approximately 65C.

EXAMPLE XIII Preparation of the Di Ester from 2-PhenyIazo-2-cyano- S-hydroxypentane and Trans-4,4-Azobis(4- cyanovaleryl chloride) 7 CH8 0 CH3 l c C H OC-; A

from Example V) and 4 ml. of pyridine in 25 ml. of benzene was added 5.1 g. (.0162 moles) of trans-4,4-azobis(4- cyanovaleryl chloride) holding the temperature at 25C. i C. The reaction was stirred an additional 3 hours and the pyridine hydrochloride filtered off. The benzene filtrate was washed with 5% I-ICI and then with water until neutral. The benzene solution was dried over anhydrous sodium sulfate, filtered and the benzene removed on a rotating evaporator leaving 10.9 g. (99% yield) of a brown viscous liquid whose infrared spectrum was in agreement with that of the desired product.

The two phenyl azo portions of the molecule have l0 hour half-lives at approximately 130C. while the symmetrical azonitrile portion of the molecule has a 10 hour half-life at approximately C.

EXAMPLE XIV Block Copolymerization of Styrene and Methyl Methacrylate with the Sequential Azo Initiator of Example III A. Preparation of an Azo-Containing Polystyrene the Ester of Z-Hydroxyethyl t- To a solution of 7.0 g. (0.0323 moles) of 2- phenyla2o-2-cyano-5-hydroxypentane (prepared as in A w ws-t Butylazocarboxylate and 4-t-Butylazo-4-cyanovaleryl Chloride of Example lll: 

1. AN AZO COMPOUND OF THE FORMULA:
 2. An azo compound as in claim 1 where B is -C(O)O- and A and A'' are -C(R2) (Z)R5-.
 3. 